Sports Cards Pricing/Value....

I know these threads used to come up ever so often, but it's been a while since I've seen one. Anyway, just came across ALL of my old cards. I was a huge nerd about it growing up and kept them very well organized and of course in mint condition. Of course 50% or more of my collection comes from the extremely over saturated market of the late 80's early 90's, but I also have a good percentage of gems going back to the 60's and 70's.

Today, I have no clue how to estimate their value. My last becket dates back to like 93. I was wondering if maybe there is some awesome, universal price guide I could find somewhere on the intrawebz to help me get an idea of what I'm looking at. Been kind if googling certain cards and getting eBay prices, but those vary hugely. I have a friend that's very interested in buying a majority of them, and although the more I look at them and realize that they almost have a priceless, nostalgic value to me.... I'd still love to know what they'd be worth to someone else from a buyers standpoint.

I know all things being perfect, they have to be worth at least upwards of 10 G's that would maybe fetch 10% of that on a good day. I thought about throwing out a random # like $500 for all of it, but I'm afraid one day I'd regret it if I ever had a son I could pass them down to. I'm not desperate for money or anything, so it's really just something to think about. Any of you ever went through a similar situation?